Diversity and relative abundance of corals, octocorals and sponges at Jaragua National Park, Dominican Republic

The Jaragua National Park is located in a remote area to the SW coast of the Dominican Republic. Fishing and mining are the major human activities. The main reef formations of the Park include: (a) long bank reefs (spur and groove) growing as bands over the platform and running in a SW-NW direction at 12-25 m depth, (b) well developed, deep, fringing reefs at the platform edge (drop-off) areas which could extend from 10 to 45 m depth, and (c) small patch reefs and poorly developed coral-octocoral-sponge-algal communities in shallow platforms near shore, rocky bottoms, and over the submerged walls of the uplifted reef. Nine reef localities were surveyed between Cabo Beata and Bahia Honda using Scuba diving to inventory the diversity and relative abundance of scleractinian corals, octocorals and sponges. Fringing reefs were surveyed starting at the bottom (30 m) and swimming in a zig-zag pattern (50 m on each side) to shallower areas. Bank reefs were surveyed by swimming in zig-zag across the spur-groove formation along 500 m. Sponges were the most diverse group with 83 species in 50 genera followed by the scleractinian corals with 56 species in 26 genera and the octocorals with 47 species in 15 genera. New records included eight coral species, 29 octocoral species and 59 sponges. The diversity, species composition and abundance of particular groups varied across the different localities. Northern reefs within the park and the Los Frailes Island offshore had the highest live cover, relative abundance and diversity for the three groups. In general, the Jaragua National Park had the highest diversity of corals, octocorals and sponges reported for the Dominican Republic and rank amongst the highest reported for the northern Caribbean. It is recommended that the area be protected and that fishing activities be regulated or eliminated altogether.     

Competitive interactions between corals and Trididemnum solidum on Mexican Caribbean reefs

The ascidian Trididemnum solidum competes for space on Caribbean reefs and is capable of overgrowing live scleractinian corals. From 2006 to 2009, we monitored over 30,000 coral colonies and quantified competitive interactions with this ascidian at four reef sites along the Mexican Caribbean. The total number of competitive interactions increased in time, but the mean percentage of coral colonies involved in interactions remained lower than 1% in all reefs. Bottom cover by T. solidum was also low (mean < 0.5%) in all reef sites in all sampling years. We conclude that during the temporal scope of our study, the overall potential effect of T. solidum on the dynamics of Mexican Caribbean coral populations was minimal.     

High macroalgal cover and low coral recruitment undermines the potential resilience of the world's southernmost coral reef assemblages

Coral reefs are under increasing pressure from anthropogenic and climate-induced stressors. The ability of reefs to reassemble and regenerate after disturbances (i.e., resilience) is largely dependent on the capacity of herbivores to prevent macroalgal expansion, and the replenishment of coral populations through larval recruitment. Currently there is a paucity of this information for higher latitude, subtropical reefs. To assess the potential resilience of the benthic reef assemblages of Lord Howe Island (31°32'S, 159°04'E), the worlds' southernmost coral reef, we quantified the benthic composition, densities of juvenile corals (as a proxy for coral recruitment), and herbivorous fish communities. Despite some variation among habitats and sites, benthic communities were dominated by live scleractinian corals (mean cover 37.4%) and fleshy macroalgae (20.9%). Live coral cover was higher than in most other subtropical reefs and directly comparable to lower latitude tropical reefs. Juvenile coral densities (0.8 ind.m(-2)), however, were 5-200 times lower than those reported for tropical reefs. Overall, macroalgal cover was negatively related to the cover of live coral and the density of juvenile corals, but displayed no relationship with herbivorous fish biomass. The biomass of herbivorous fishes was relatively low (204 kg.ha(-1)), and in marked contrast to tropical reefs was dominated by macroalgal browsing species (84.1%) with relatively few grazing species. Despite their extremely low biomass, grazing fishes were positively related to both the density of juvenile corals and the cover of bare substrata, suggesting that they may enhance the recruitment of corals through the provision of suitable settlement sites. Although Lord Howe Islands' reefs are currently coral-dominated, the high macroalgal cover, coupled with limited coral recruitment and low coral growth rates suggest these reefs may be extremely susceptible to future disturbances.     

The dynamics of architectural complexity on coral reefs under climate change

One striking feature of coral reef ecosystems is the complex benthic architecture which supports diverse and abundant fauna, particularly of reef fish. Reef‐building corals are in decline worldwide, with a corresponding loss of live coral cover resulting in a loss of architectural complexity. Understanding the dynamics of the reef architecture is therefore important to envision the ability of corals to maintain functional habitats in an era of climate change. Here, we develop a mechanistic model of reef topographical complexity for contemporary Caribbean reefs. The model describes the dynamics of corals and other benthic taxa under climate‐driven disturbances (hurricanes and coral bleaching). Corals have a simplified shape with explicit diameter and height, allowing species‐specific calculation of their colony surface and volume. Growth and the mechanical (hurricanes) and biological erosion (parrotfish) of carbonate skeletons are important in driving the pace of extension/reduction in the upper reef surface, the net outcome being quantified by a simple surface roughness index (reef rugosity). The model accurately simulated the decadal changes of coral cover observed in Cozumel (Mexico) between 1984 and 2008, and provided a realistic hindcast of coral colony‐scale (1–10 m) changing rugosity over the same period. We then projected future changes of Caribbean reef rugosity in response to global warming. Under severe and frequent thermal stress, the model predicted a dramatic loss of rugosity over the next two or three decades. Critically, reefs with managed parrotfish populations were able to delay the general loss of architectural complexity, as the benefits of grazing in maintaining living coral outweighed the bioerosion of dead coral skeletons. Overall, this model provides the first explicit projections of reef rugosity in a warming climate, and highlights the need of combining local (protecting and restoring high grazing) to global (mitigation of greenhouse gas emissions) interventions for the persistence of functional reef habitats.     

Anthropogenic mortality on coral reefs in Caribbean Panama predates coral disease and bleaching

Caribbean reef corals have declined precipitously since the 1980s due to regional episodes of bleaching, disease and algal overgrowth, but the extent of earlier degradation due to localised historical disturbances such as land clearing and overfishing remains unresolved. We analysed coral and molluscan fossil assemblages from reefs near Bocas del Toro, Panama to construct a timeline of ecological change from the 19th century-present. We report large changes before 1960 in coastal lagoons coincident with extensive deforestation, and after 1960 on offshore reefs. Striking changes include the demise of previously dominant staghorn coral Acropora cervicornis and oyster Dendrostrea frons that lives attached to gorgonians and staghorn corals. Reductions in bivalve size and simplification of gastropod trophic structure further implicate increasing environmental stress on reefs. Our paleoecological data strongly support the hypothesis, from extensive qualitative data, that Caribbean reef degradation predates coral bleaching and disease outbreaks linked to anthropogenic climate change.     

Caribbean reef coral diversity during the early to middle Miocene: an example from the Anguilla Formation

Reefal units in the early to middle Miocene of Anguilla consist of small, irregular lenses of variable coral composition which developed on a shallow, isolated offshore carbonate platform. They are composed of three distinct coral biofacies (branched, mound-shaped, and platy), which are haphazardly distributed in association with inter-reef sands. These units most probably formed as patch reefs across a broad, shallow area that was exposed to moderate energy conditions and periodically affected by storms. No evidence supports the existence of a more extensive barrier reef system. Comparisons with Oligocene and Mio-Pliocene reefs suggest that during the early to middle Miocene, Caribbean reefs were generally smaller in size (<100 m³) and lower in diversity (21 species in Anguilla, 42 species in total across the Caribbean) than Caribbean reefs during the late Oligocene or during the ate Miocene to early Pliocene (71 species in the Dominican Republic, 80 species total across the Caribbean). The early to middle Miocene Caribbean reef coral fauna was dominated by nine widespread species that occur in deposits of similar age in both Anguilla and Panama. More than half of the fauna consisted of Oligocene relicts. Of the 21 genera that first appeared in the Caribbean during Miocene time, 14 had first occurrences after the middle Miocene, as barrier reef systems became more prevalent across the central Caribbean.     

Cyclone effects on coral reef habitats in New Caledonia (South Pacific)

The impacts of the unusually strong Cyclone Erica (March 2003) on coral reef habitats at a site located on the northwest coast of New Caledonia (South Pacific) were assessed using a 6-year data set (2002–2007). We examined the interannual variations of key variables describing reef habitats (live hard and soft corals, dead corals in place, coral debris, algae and relative proportion of mechanically vulnerable and resistant live hard corals). The cyclone-induced disturbances of habitats differed according to three reef types: patch reefs, barrier reefs far from passes (more than 3 km from the nearest pass) and barrier reefs near passes (less than 3 km from the nearest pass). Short-term mechanical damage was detected on the three-dimensional structure of reef habitats with a notable shift from a community dominated by mechanically vulnerable corals to one dominated by resistant corals on barrier reefs far from passes. The history of habitats and their pre-disturbance characteristics, in link with local hydrodynamics, was found to influence their short-term susceptibility to extreme events such as cyclones. However, the most significant effects appeared in the midterm (within 2 years after the cyclone) as the cover of live hard corals significantly decreased by approximately 45% between 2002 and 2004 on all reef types. The short- and midterm disturbances of coral reef habitats are discussed with regard to published temporal variations in reef fish assemblages, underlining the delayed effects of this cyclonic event on fish as well as benthic habitats. Coral reef habitats and live corals had shown significant patterns of recovery 4 years after the cyclone, followed by similar recovery in fish community, suggesting good resilience in a face of this major natural disturbance in an area under moderate anthropogenic pressure.     

Shifting ecological baselines and the demise of Acropora cervicornis in the western North Atlantic and Caribbean Province: a Pleistocene perspective

 In recent years, marine scientists have become increasingly alarmed over the decline of live coral cover throughout the Caribbean and tropical western Atlantic region. The Holocene and Pleistocene fossil record of coral reefs from this region potentially provides a wealth of long-term ecologic information with which to assess the historical record of changes in shallow water coral reef communities. Before fossil data can be applied to the modern reef system, critical problems involving fossil preservation must be addressed. Moreover, it must be demonstrated that the classic reef coral zonation patterns described in the early days of coral reef ecology, and upon which “healthy” versus “unhealthy” reefs are determined, are themselves representative of reefs that existed prior to any human influence. To address these issues, we have conducted systematic censuses of life and death assemblages on modern “healthy” patch reefs in the Florida reef tract that conform to the classic Caribbean model of reef coral zonation, and a patch reef in the Bahamas that is currently undergoing a transition in coral dominance that is part of a greater Caribbean-wide phenomenon. Results were compared to censuses of ancient reef assemblages preserved in Pleistocene limestones in close proximity to each modern reef. We have determined that the Pleistocene fossil record of coral reefs may be used to calibrate an ecological baseline with which to compare modern reef assemblages, and suggest that the current and rapid decline of Acropora cervicornis observed on a Bahamian patch reef may be a unique event that contrasts with the long-term persistence of this taxon during Pleistocene and Holocene time. Accepted: 19 May 1998     

Ecological condition of coral reef assemblages in the Cuban Archipelago

The condition of coral reefs in the Cuban Archipelago is poorly known. We aimed to analyse coral assemblages across 199 reef sites belonging to 12 localities. Crest and fore reefs were assessed using six metrics: species richness, density, coral cover, mortality, coral size and reef complexity. The condition of reefs varied across the archipelago from healthy to depleted reefs. The localities with best scores were Cienfuegos, Bahía de Cochinos and Cazones. These reefs have values of living coral cover (>20%) and complexity (>50?cm) similar to the best preserved Caribbean reefs. However, the majority of crest biotopes suffered important deterioration with old mortality of Acropora palmata populations and moderate coral cover (15%); although crest reefs still maintained their structural complexity. Despite moderate levels of coral cover in fore reefs (18%), their condition was alarming because 25% of the sites had cover below the recovery threshold of 10%, accumulated mortality and structural flattening. Compared with the 1980s, the species richness was roughly the same (42) for crest and fore reefs, although dominance has changed to widespread tolerant species. Coral reef assemblages varied at local and regional scales in similar magnitude, suggesting the combined effects of natural and anthropogenic drivers.     

Region‐wide temporal and spatial variation in Caribbean reef architecture: is coral cover the whole story?

The architectural complexity of coral reefs is largely generated by reef‐building corals, yet the effects of current regional‐scale declines in coral cover on reef complexity are poorly understood. In particular, both the extent to which declines in coral cover lead to declines in complexity and the length of time it takes for reefs to collapse following coral mortality are unknown. Here we assess the extent of temporal and spatial covariation between coral cover and reef architectural complexity using a Caribbean‐wide dataset of temporally replicated estimates spanning four decades. Both coral cover and architectural complexity have declined rapidly over time, with little evidence of a time‐lag. However, annual rates of change in coral cover and complexity do not covary, and levels of complexity vary greatly among reefs with similar coral cover. These findings suggest that the stressors influencing Caribbean reefs are sufficiently severe and widespread to produce similar regional‐scale declines in coral cover and reef complexity, even though reef architectural complexity is not a direct function of coral cover at local scales. Given that architectural complexity is not a simple function of coral cover, it is important that conservation monitoring and restoration give due consideration to both architecture and coral cover. This will help ensure that the ecosystem services supported by architectural complexity, such as nutrient recycling, dissipation of wave energy, fish production and diversity, are maintained and enhanced.     

Non-colonial coral macro-borers as indicators of coral reef status in the South Pacific of Costa Rica

Coral reef status was surveyed in three south Pacific coral reefs of Costa Rica, one in Ca?o Island and two in Golfo Dulce, and the density, richness and distribution of non-colonial macro borers (> 1 mm) was determined in dead and live coral fragments from these reefs. Based upon traditional indicators of degradation such as high particulate suspended matter and low live coral cover, the reefs at Ca?o Island are in better condition than those at Golfo Dulce. Reef degradation in Golfo Dulce is mainly due to high loads of terrestrial sediments as a consequence of watersheds deforestation. In this study, 36 coral boring species are reported for the eastern Pacific. At the family level, there is high endemism (10%) and greater affinity with the Indo-Pacific (34%), as compared with the eastern Atlantic and Mediterranean (29%) and western Atlantic and Caribbean (27%). The dominant non-colonial macro boring families at the study reefs are mytilid bivalves, eunicid polychaetes and aspidosiphonid sipunculans, with the bivalves considered the main internal bioeroders due to their greater body size and abundances. The level of mortality of the coral colonies and the general level of reef degradation influenced the composition of non-colonial macro-borers. Diversity and total macro-borer density, especially aspidosiphonid density, is higher in corals with greates dead than live cover. In the healthiest coral colonies (less than 50% of partial mortality), mytilids domination, macro-borer diversity and total density, is higher in Golfo Dulce, where reefs are more degraded. In the most affected coral colonies (more than 50% dead), macro-borers total density, especially aspidosiphonids density, is higher, of the healthiest reef of this study, Platanillo. Bivalve relative abundance increases and sipunculan relative abundance decreases with increasing site degradation. In conclusion bioeroder variables can also be used as reef health indicators.     

Live coral repels a common reef fish ectoparasite

Coral reefs are undergoing rapid changes as living corals give way to dead coral on which other benthic organisms grow. This decline in live coral could influence habitat availability for fish parasites with benthic life stages. Gnathiid isopod larvae live in the substratum and are common blood-feeding parasites of reef fishes. We examined substrate associations and preferences of a common Caribbean gnathiid, Gnathia marleyi. Emergence traps set over predominantly live coral substrata captured significantly fewer gnathiids than traps set over dead coral substrata. In laboratory experiments, gnathiids preferred dead coral and sponge and tended to avoid contact with live coral. When live gnathiids were added to containers with dead or live coral, significantly fewer were recovered from the latter after 24 h. Our data therefore suggest that live coral is not suitable microhabitat for parasitic gnathiid isopods and that a decrease in live coral cover increases available habitat for gnathiids.     

Regional‐scale dominance of non‐framework building corals on Caribbean reefs affects carbonate production and future reef growth

Coral cover on Caribbean reefs has declined rapidly since the early 1980's. Diseases have been a major driver, decimating communities of framework building Acropora and Orbicella coral species, and reportedly leading to the emergence of novel coral assemblages often dominated by domed and plating species of the genera Agaricia, Porites and Siderastrea. These corals were not historically important Caribbean framework builders, and typically have much smaller stature and lower calcification rates, fuelling concerns over reef carbonate production and growth potential. Using data from 75 reefs from across the Caribbean we quantify: (i) the magnitude of non‐framework building coral dominance throughout the region and (ii) the contribution of these corals to contemporary carbonate production. Our data show that live coral cover averages 18.2% across our sites and coral carbonate production 4.1 kg CaCO₃ m^?2 yr^?1. However, non‐framework building coral species dominate and are major carbonate producers at a high proportion of sites; they are more abundant than Acropora and Orbicella at 73% of sites; contribute an average 68% of the carbonate produced; and produce more than half the carbonate at 79% of sites. Coral cover and carbonate production rate are strongly correlated but, as relative abundance of non‐framework building corals increases, average carbonate production rates decline. Consequently, the use of coral cover as a predictor of carbonate budget status, without species level production rate data, needs to be treated with caution. Our findings provide compelling evidence for the Caribbean‐wide dominance of non‐framework building coral taxa, and that these species are now major regional carbonate producers. However, because these species typically have lower calcification rates, continued transitions to states dominated by non‐framework building coral species will further reduce carbonate production rates below ‘predecline’ levels, resulting in shifts towards negative carbonate budget states and reducing reef growth potential.     

Can Coral Cover be Restored in the Absence of Natural Recruitment and Reef Recovery?

With many coral reef areas being degraded whether by anthropogenic or natural causes, a search is on for resilient species of corals that can restore coral cover where needed, if coral reefs are to continue to provide adequate ecosystem services. A series of experiments were undertaken in two sites with different environmental attributes and substrates in a lagoonal area in the northwestern Philippines to test the potentials of a local species, Porites cylindrica, for reef rehabilitation. With the use of asexual fragmentation of donor colonies, different treatments were tested, particularly to determine if the species would survive on different substrates, that is, solid, massive versus digitate/anastomosing, dead colonies. The results after nearly 2 years of the experiment were extraordinarily successful, with survival of transplants ranging from a high of 98% to a low of 80% of colonies, resulting in extensive coral cover on both original and new or different substrate from the original. A subsequent observation after another 16 months showed the coral cover to have been complete or nearly complete in the experimental plots, with the transplanted colonies fusing, and with evident reef fish communities where there were none before. Had there been no intervention, it is highly likely that the reefs would have remained in a degraded state .     

Caribbean reefs of the Anthropocene: Variance in ecosystem metrics indicates bright spots on coral depauperate reefs

Dramatic coral loss has significantly altered many Caribbean reefs, with potentially important consequences for the ecological functions and ecosystem services provided by reef systems. Many studies examine coral loss and its causes—and often presume a universal decline of ecosystem services with coral loss—rather than evaluating the range of possible outcomes for a diversity of ecosystem functions and services at reefs varying in coral cover. We evaluate 10 key ecosystem metrics, relating to a variety of different reef ecosystem functions and services, on 328 Caribbean reefs varying in coral cover. We focus on the range and variability of these metrics rather than on mean responses. In contrast to a prevailing paradigm, we document high variability for a variety of metrics, and for many the range of outcomes is not related to coral cover. We find numerous “bright spots,” where herbivorous fish biomass, density of large fishes, fishery value, and/or fish species richness are high, despite low coral cover. Although it remains critical to protect and restore corals, understanding variability in ecosystem metrics among low‐coral reefs can facilitate the maintenance of reefs with sustained functions and services as we work to restore degraded systems. This framework can be applied to other ecosystems in the Anthropocene to better understand variance in ecosystem service outcomes and identify where and why bright spots exist.     

Measuring coral reef decline through meta-analyses

Coral reef ecosystems are in decline worldwide, owing to a variety of anthropogenic and natural causes. One of the most obvious signals of reef degradation is a reduction in live coral cover. Past and current rates of loss of coral are known for many individual reefs; however, until recently, no large-scale estimate was available. In this paper, we show how meta-analysis can be used to integrate existing small-scale estimates of change in coral and macroalgal cover, derived from in situ surveys of reefs, to generate a robust assessment of long-term patterns of large-scale ecological change. Using a large dataset from Caribbean reefs, we examine the possible biases inherent in meta-analytical studies and the sensitivity of the method to patchiness in data availability. Despite the fact that our meta-analysis included studies that used a variety of sampling methods, the regional estimate of change in coral cover we obtained is similar to that generated by a standardized survey programme that was implemented in 1991 in the Caribbean. We argue that for habitat types that are regularly and reasonably well surveyed in the course of ecological or conservation research, meta-analysis offers a cost-effective and rapid method for generating robust estimates of past and current states.     

Coral-algal competition on damaged reefs

Natural and anthropogenic catastrophes occurred at the end of the previous and in the beginning of the current centuries at the coral reefs of the World Ocean, and their consequences for the tropical shelf ecosystems have been described based on published data and our own investigations. It has been shown that in recent decades coral populations on reefs of tropical and subtropical regions of the World Ocean have been reduced by 80%, and in some areas have completely vanished. The biodiversity of reef ecosystems has been considerably reduced. The main reason for such changes is a 1-2°C increase in the temperature of surface waters in comparison with the monthly mean temperature in the hot season. The fate of the damaged coral reefs is under discussion. It is thought that in clean waters partially damaged coral reefs can recover, whereas in waters polluted as the result of human activity they collapse. The rate of coral reef restoration depends on the hydrological and hydrochemical conditions, frequency of natural calamities and competitive interrelation of algae and corals on the damaged sites of coral reefs. The nature of competitive interrelation between algae and corals is considered, viz., the dynamics of obliteration of damaged and dead coral colonies by various algal species, mechanisms of competitive interrelation, effects of the environment on the competitive ability of corals and algae, the internal and external conditions for victory in competitive activity. It has been suggested that coral reefs can be restored through temporary transformation into a vegetable reef. In the absence of natural calamities damaged reefs can be clearly restored to their original or altered state over several decades, but only in clean waters.     

Changes in Coral Reef Communities and an Associated Reef Fish Species, <Emphasis Type="Italic">Cephalopholis cruentata</Emphasis> (Lacépède), After 30 years on Curaçao (Netherlands Antilles)

Using the same methodology and identical sites, we repeat a study dating from 1973 and quantify cover of hard coral species, soft corals, sponges, hard substratum and soft substratum, and density of a commercially important reef fish species, the graysby Cephalopholis cruentata, along a depth-gradient of 3–36 m on the coral reefs of Curaçao. The objective was to determine the multi-decade change in benthic coral reef cover and structural complexity, and their effect on densities of an associated reef fish species. Total hard coral cover decreased on average from 52% in 1973 to 22% in 2003, representing a relative decline of 58%. During this time span, the cover of hard substratum increased considerably (from 11 to 58%), as did that of soft corals (from 0.1 to 2.2%), whereas the cover of sponges showed no significant change. Relative decline of hard coral cover and of reef complexity was greatest in shallow waters (near the coast), which is indicative of a combination of anthropogenic influences from shore and recent storm damage. Cover of main reef builder coral species (Agaricia spp., Siderastrea siderea, Montastrea annularis) decreased more than that of other species, and resulted in a significant decrease in reef complexity. Although density of C. cruentata was highly correlated to cover of Montastrea and Agaricia in 1973, the loss of coral cover did not show any effect on the total density of C. cruentata in 2003. However, C. cruentata showed a clear shift in density distribution from shallow water in 1973 to deep water in 2003. It can be concluded that the reefs of Curaçao have degraded considerably in the last three decades, but that this has had no major effect on the population size of one commercially important coral-associated fish species.     

Coral reef resilience to thermal stress in the Eastern Tropical Pacific

Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios.     

Conservation genetics and the resilience of reef-building corals

Coral reefs have suffered long-term decline due to a range of anthropogenic disturbances and are now also under threat from climate change. For appropriate management of these vulnerable and valuable ecosystems it is important to understand the factors and processes that determine their resilience and that of the organisms inhabiting them, as well as those that have led to existing patterns of coral reef biodiversity. The scleractinian (stony) corals deposit the structural framework that supports and promotes the maintenance of biological diversity and complexity of coral reefs, and as such, are major components of these ecosystems. The success of reef-building corals is related to their obligate symbiotic association with dinoflagellates of the genus Symbiodinium. These one-celled algal symbionts (zooxanthellae) live in the endodermal tissues of their coral host, provide most of the host's energy budget and promote rapid calcification. Furthermore, zooxanthellae are the main primary producers on coral reefs due to the oligotrophic nature of the surrounding waters. In this review paper, we summarize and critically evaluate studies that have employed genetics and/or molecular biology in examining questions relating to the evolution and ecology of reef-building corals and their algal endosymbionts, and that bear relevance to coral reef conservation. We discuss how these studies can focus future efforts, and examine how these approaches enhance our understanding of the resilience of reef-building corals.